Google is making this move due to security concerns.

Starting February 13, you won't be able to send any JavaScript files via Gmail as Google is blocking them due to safety concerns. That said, users won't be able to send any .js files using Gmail and Google will be scanning the zip archive files, and if they find any .js file archived, then the user won't be able to send that as well.

However, Google claims that users can share or send the JavaScript (.js) files via any cloud storage services including the company's own Google Drive. For the unknown, JavaScript is used to develop web-based applications, and they run alongside a web page. However, if a JavaScript file is opened on a Windows system, there might be a possibility that the system will be infected with malicious files.

Also, from February 13, Gmail will notify an error saying that it can't send the .js files. To recall, Google already blocked the Windows executable files (.exe) and batch files (.bat) a long time ago.